As a heat source for warming up a conventional fuel evaporator 100 or 200, an electric heater 101 shown in FIG. 6A and a combustion burner 201 shown in FIG. 6B are known. A warm-up method with the electric heater 101 or the combustion burner 201 is carried out either by directly or indirectly heating the fuel evaporator. In the indirect heating, gas or liquid is heated by a heat source, such as the electric heater 101, and the heated gas or liquid is used as a heat transfer medium.
For example, Japanese Laid-open Patent Publication No. Hei 11-86893 discloses a warming up method, in which fuel is burned with a combustion burner to generate heat, and a heat exchanger utilizes the resulting heat for raising the temperature of a raw material.
Further, the applicant discloses a warm-up apparatus in Japanese Patent Application No. Hei 11-315996 (unpublished). The warm-up apparatus is equipped with a catalyst combustor for generating a gas for raising the temperature of the raw material. The electric heater 101 shown in FIG. 6A and the combustion burner 201 shown in FIG. 6B are used for raising the temperature of the catalyst combustor.
However, when the flow rate of the exhaust gas (also referred to as an “off gas”) flowing in the piping becomes greater, electric power consumption becomes greater in the case of heating with the electric heater 101. Meanwhile, in the case of heating with the combustion burner 201, there are problems, such as increasing amount of the exhaust gas of the combustion burner 201 and increasing size of the burner itself.
However, because both of the above warm-up methods are poor in heating efficiency, it takes time for completing the warming-up of the fuel evaporator 100 or 200 after actuating or starting the warm-up apparatus.
In order to eliminate the foregoing drawbacks of the prior art, the present invention seeks to provide a method of warming up a fuel evaporator, which ensures a quick and reliable warm-up operation from the start of the warm-up apparatus to the end of the operation.